Spark plug



' .July 14, 1936. c. A. XA-RDELL SPARK PLUG Filed Feb. 20, 1934 luv w;

Patented July 14, 1936 PATENT OFFICE SPARK PLUG Charles A. We, mm. N.Y., assignor of one-half to Charles Coupe, Utica, N. Y.

Application February 20, 1934, Serial No. 712,238 6 Claims. (Cl.123-169) In spark plugs now generally in use with internal combustionengines the main electrode extending through the central porcelainelement of the plug consists of a wire of high heat resistance 5 but oflow conductivity for the passage of the electric current. While it isdesirable that the spark plug should have a high current strength thiscurrent strength is largely reduced by the high current resistance ofthese heat resisting l electrodes. Also, owing to the high heatresulting from the low electrical conductivity of these electrodes, they-are liable to burn out .or become rapidly deteriorated by pitting orotherwise.

This invention has for its object to produce a 15 spark plug which willafford a high current strength but which will not be liable to burn outor become pitted or otherwise deteriorated and thus it will have greatdurability and long, emcient life. To this end, according to the present20 invention, the main electrode of the spark plug,

which extends through the central porcelain element of the plug,consists of a wire having a heat resisting core of low electricalconductivity, said core being cased or covered with a heat-resisting 25laminated casing of high electrical conductivity. This laminated casingor covering will preferably be of copper or silver, and a heat resistingcement of graphite with a binder, although powdered carbon or a suitablepowdered metal of high elec- 30 trical conductivity may be used in thecement if desired.

To transfer heat from the main electrode through the central porcelainelement of the outside shell of the plug a gasket or gaskets of cop- 3per will preferably be interposed between said porcelain element andsaid outside shell, thus somewhat cooling said main electrode, andreducing any tendency of its burning out.

In the accompanying drawing Fig. 1 is a ver- 40 tical section of a sparkplug embodying the present invention.

Fig. 2 is an enlarged fragmentary section of the main electrode.

Referring to the drawing, l2 denotes the outer 45 shell or body of thespark plug having a threaded part I! to enable it to be screwed inworking position, as usual. This shell or body I2 is of copper alloy ofhigh heat transfer value or high heat conductivity, this alloy beingpreferably of about 50 80% copper with the balance of zinc, tin, leadand a small percentage of silver. The proportions of this alloy may, ofcourse, be varied somewhat to vary the heat transfer value thereof.

The central insulating porcelain element I3 is 55 secured intheshell orbody I: bya nut M which will preferably be of a copper alloy similar tosaid shell or body l2. Interposed between the lower part of the shell orbody I! and the central porcelain element is is a copper gasket orferrule I! of considerable length and a smaller 5 gasket I6 ispreferably also interposed between the lower end of the nut i4 and thesaid porcelain body. These gaskets make air-tight joints at the placeswhere they are located and serve to transfer heat from the porcelainbody to the outer 10 parts.

Extending through the porcelain element I3 is a main electrode l'lconsisting of a core ll of low electrical conductivity but which is of ahigh heat resisting alloy of nickel and chromium. This core has a.coating or casing l8 of copper outside of which is a coating or casingI! of silver, thus afiording a laminated construction of high electricalconductivity and high heat resistance. These elements i8 and I9 areincontact with each other, as clearly shown in Fig. 2. This laminatedelectrode is secured in the porcelain member by a heat resisting cement20 of high electrical conductivity and high heat resisting quality, saidcement being preferably of graphite with a suitable binder althoughpowdered carbon or a suitable powdered metal may be used instead of thegraphite. This main electrode is provided at its upper part with ascrew-threaded part 2i by which it is affixed in the porcelain elementii in suitable relation to the auxiliary electrode 22 carried by theshell or body l2.

From the foregoing it will be apparent that the improved constructionaffords a spark plug comprising a main electrode having a heat resistingcore of low electrical conductivity but with a laminated casing of highelectrical conductivity and a high heat resisting character and fromwhich more or less heat is conducted through the central porcelain bodyto the outer parts of the plug, thus tending to cool said main electrodesomewhat and thereby extending its life.

Having thus described my invention I claim and desire to secure byLetters Patent:

1. A spark plug having a main electrode comprising a heat resisting coreof low electrical conductivity covered by a laminated heat-resistingcovering or casing of high electrical conductivity.

2. A spark plug having a main electrode comprising a heat-resisting coreof low electrical conductivity covered by a laminated heat-resistingcovering or casing of high electrical conductivity, said laminatedcovering or casing consisting of a layer of copper next said core andeiicioaed in a layer of silver.

3. A spark plug having a main electrode comprising a heat-resisting'coreof low electrical conductivity covered by a laminated heat-resistingcovering or casing of high electrical conductivity, said spark plugcomprising a non-conducting element and a heat-resisting cement 01. highelectrical conductivity and by which said electrode is secured in saidelement.

4. A spark plug having a main electrode comprising a heat resisting coreof low electrical conductivity covered by a laminated heat-resistingcovering or casing of high electrical conductivity,

said laminated covering or casing consisting oi. a layer of copper nextsaid core and enclosed in a layer of silver, said spark plug comprisinga nonconducting element and a heat-resisting cement of high electricalconductivity and by which said electrode is secured in said element.

5. A spark plug comprising an outer shell or body of a copper alloy, aporcelain element, a

copper alloy nut to secure said porcelain element in said shell or body,and a main electrode having a laminated casing extending through saidporcelain element.

6. A spark plug comprising an outer shell or body or copper alloy, aporcelain element, a copper alloy nut to secure said porcelain elementin said shell or body, and a main electrode having a laminated casingextending through said porcelain element, said spark plug alsocomprising a long copper gasket or ferrule interposed between saidporcelain element and said outer shell or body.

CHARLES A. XARDELL.

